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Not applicable.
While the present invention may be employed in several different off-highway applications, in order to simplify this explanation, the present invention will be described in the context of an exemplary agricultural tractor and associated cab.
Today, in farming, as in other industries, competitive pressures have forced farmers to search for ways in which to increase efficiency and productivity. One obvious way to increase efficiency and productivity is to use better and more efficient equipment such as state of the art agricultural tractors or combines. A properly configured tractor appreciably increases the speed with which farmers can plant, till, fertilize and harvest.
One other way in which to increase efficiency and productivity is to employ highly specialized equipment to perform certain farming tasks. For instance, some specialized tractors are equipped with sprayers or other chemical spreading implements that apply pesticides and other noxious products within fields extremely efficiently.
Unfortunately, state of the art tractors are relatively expensive and therefore, in order to justify the costs associated with such tractors, even though the tractors reduce the time required to perform various tasks, farmers must spread the costs of such equipment over increasingly larger enterprises. In farming, a larger enterprise typically translates, at least in part, into farming more acreage and, not surprisingly, farming more acreage typically requires a greater time commitment on the part of the farmer.
In the case of specialized equipment such as sprayer equipped tractors and the like, high costs associated with that equipment and limited uses for the equipment renders it difficult for some farmers to purchase their own such equipment. Instead, a segment of the service industry has evolved around specialized types of equipment where a single owner purchases such equipment and provides services to many farmers within an area so that, again, the cost of the equipment is spread out among many farmers and their acreage.
Because farmers and special service providers are spending greater amounts of time in their tractor cabs, cab comfort has become a relatively important feature in new tractor configuration. Thus, new tractors are typically fitted with state of the art cabs including ergonomically designed seating and controls, better lines of sight and cab space conditioning systems that control temperature, air circulation and humidity.
In addition to the features described above, the industry has also recognized that air quality within the cab space is important to operator comfort and health and also to overall system efficiency. To this end, in many applications, agricultural tractors operate in environments that include high concentrations of airborne dirt and dust. Moreover, where a tractor implement is used to spray or apply a noxious chemical, portions (e.g., droplets or particles) of the noxious chemicals often become airborne and can be inhaled by a tractor operator. Hereinafter airborne particles within an environment will collectively be referred to as xe2x80x9ccontaminantsxe2x80x9d.
Inhaling contaminants can cause discomfort over short periods of time and, over long periods of time, can lead to other medical symptoms. Moreover, contaminants have been known to accumulate on heating and cooling system components and reduce both efficiency and effectiveness, thereby further reducing operator comfort.
To minimize contaminants (e.g., dirt, dust, etc.) within the cab space, it is well known to provide a completely enclosed cab and an air circulation system that takes in and filters xe2x80x9cfreshxe2x80x9d outside air from the ambient, heats or cools the air via an atmosphere control system and circulates the conditioned air within the cab via one or more pressurization blowers/fans. Preferably, cab air pressure is maintained above a threshold pressure that is slightly higher than atmospheric pressure (i.e., at least a few millimeters of head of water). The pressure differential between the ambient and threshold pressure inhibits entry of contaminants into the cab through, for example, imperfectly sealed doors or windows.
To increase cooling and heating efficiency, many tractor air conditioning systems will include two separate fans. In two fan systems, a first fan is typically positioned downstream of the air inlet and filter for drawing fresh air into the conditioning system from the outside ambient while a second recirculating fan is positioned downstream of a system inlet located within the cab for drawing air into the conditioning system from within the cab. The recirculating fan, as the name implies, recirculates air from within the cab through the conditioning unit. In two fan systems, the recirculated and fresh air are combined within the conditioning unit prior to being directed into the cab space. Because the recirculated air is already generally at the temperature and humidity level required inside the cab space, the system capacity required to condition the recirculated air is relatively less than the system capacity required to condition fresh air and therefore overall conditioning efficiency is increased.
Unfortunately, under certain circumstances, a cab conditioning system is rendered incapable of maintaining a cab pressure that is greater than the ambient pressure. For instance, over time, cab door and window seals deteriorate and air escapes there through at an unexpectedly high rate thereby reducing cab pressure appreciably. As another instance, xe2x80x9cfreshxe2x80x9d air filters (i.e., filters that clean air drawn in from the outside ambient) often become clogged thereby starving the fans of inlet air and reducing cab space air pressure. As yet another example, inadvertent placement of any item in front of a blower outlet port can cause a reduction in cab pressure. Other potential causes of cab pressure drop include malfunctioning fans, improperly positioned air louvers, slightly open doors or windows, an item (e.g., a seat belt) stuck within a closed door, etc.
One solution for maintaining a desired cab pressure in spite of some of the causes of pressure drop described above has been to facilitate either manual or automatic fan speed adjustment. To this end, pressure sensors have been developed that compare ambient and cab pressures and generate alarm signals indicating when the cab pressure dips below a threshold pressure that is slightly above the ambient pressure. In the case of manually adjustable systems, the alarm signals are fed to indicators (i.e., a small light) within the cab and, when an indicator is activated, the operator is warned of the pressure problem. An operator""s manual may advise to adjust the fan speed or to modify the positions of louvers within the system plenum and duct sub-system to increase air flow.
In the case of automatically adjustable systems, the alarm signals are fed to a controller that adjusts fan speed either up or down or louver positions to maintain the cab pressure above the threshold pressure thereby maintaining cab space-ambient pressure differential yet minimizing required fresh air filtering. One exemplary automatic fan speed adjustment system is described in U.S. Pat. No. 4,581,988 (hereinafter xe2x80x9cthe ""988 patentxe2x80x9d) which issued on Apr. 15, 1986 and which is entitled xe2x80x9cProtective Device for Work in Polluted Environmentxe2x80x9d. The ""988 patent also teaches that, after increasing fan speed, if cab pressure remains below the threshold pressure, the controller activates an indicator (e.g., a small light) to warn the operator that the automatic corrective action has failed to maintain the cab space-ambient pressure differential.
In either of the manual or automatic blower speed adjustment cases, if an alarm condition occurs despite maximum fan speed, the tractor operator is supposed to recognize that the intake filter is clogged and take steps to unclog the filter. Filter unclogging may include removing a filter element and either replacing the element or cleaning the element and placing the cleaned element back into the system. Unfortunately, while advantageous, the automatic and manual pressure maintaining systems described above have several shortcomings.
First, the systems described above rely on tractor operators to take steps to correct cab pressure problems after the problems have been indicated. While operator initiative would not be a problem in some industries, as indicated above, farmers and specialized service providers often work under seemingly unreasonable time constraints and, for that reason, may elect to forego performing tasks that the farmer xe2x80x9cperceivesxe2x80x9d as unnecessary. This willingness to forego seemingly unnecessary tasks is particularly true during intense periods such as planting season, harvesting season, fertilizing times, etc., where particular tasks have to be completed within relatively short periods. Under these circumstances, an activated cab pressure light may be completely ignored as relatively unimportant (i.e., operator comfort is sacrificed for greater efficiency).
Second, even where an operator may elect to perform simple remedial tasks to increase cab pressure, the operator may be unaware that the pressure problem can be corrected via such simple tasks and therefore may forego performing the tasks. For instance, an operator may assume the cab pressure problem is due to a clogged filter that needs to be replaced which would require a trip out of the field to a maintenance location while the real problem is an improperly latched cab door. Clearly the burden of the perceived remedy affects whether or not an operator may elect to perform the remedy.
Third, even where a tractor operator responds to an activated cab pressure light, the operator may take steps to unclog the fresh air filter and, if those steps fail to deactivate the light, may assume that the light is on in error. This is especially true in systems where the threshold pressure (i.e., cab pressure) is only slightly above the outside ambient pressure as the differential, even when properly maintained, would be difficult for an operator to independently confirm.
Fourth, even where a tractor operator would think to go beyond unclogging the filter and attempt to identify some other cause of cab depressurization, the operator may not recognize every likely depressurization source, the most likely sources, the easiest sources to eliminate, etc. To this end, to avoid frustration, the operator should ideally first check the most likely sources and the easiest sources of depressurization to alleviate. Thus, checking an unlikely source of depressurization would often be a waste of time. Similarly, given two potential sources where one is difficult to alleviate and the other is relatively easy to alleviate, it makes sense to check the one that is easy to alleviate prior to the one that is difficult to alleviate as the overall time required to repressurize the cab will, on average, be less.
One solution that could aid an operator in identifying potential depressurization causes would be a trouble shooting manual that lists sources arranged as a function of likelihood and/or ease of use. Unfortunately, as in the case of most vehicle manuals, farmers often do not store manuals in cabs and therefore the manuals are not readily available when most needed (i.e., typically in a field). In addition, even if a farmer had a trouble shooting manual handy when needed, again, because of time constraints, the farmer may opt not to respond to an activated pressure indicator.
For the reasons discussed above it would be advantageous to have a system that effectively incentivizes and helps a tractor operator to take corrective action when cab space-pressure falls below a threshold pressure that is slightly above the outside ambient pressure.
It has been recognized that even a simple annoyance or disturbance during tractor operation can tip the balance in favor of taking remedial steps to correct for cab depressurization. This is particularly true in cases where the disturbance renders a tractor essentially useless for a specific purpose for even a short amount of time. For instance, disabling an implement for five minutes or until cab pressure is increased presents a tractor operator with the choice of either wasting five minutes or attempting to correct the pressure problem to reduce the duration of the disablement. Faced with such a choice, more often than not an operator will choose to at least attempt to remedy the problem. According to the present invention, balance tipping disturbances may take any of several different forms including, in addition to disabling an implement, generating an annoying alarm (e.g., audible buzz, blinking light, etc.), reducing maximum vehicle speed, etc. It has also been recognized that often, despite the existence of a relatively simple remedial step to correct a cab pressure problem, a tractor operator will ignore a pressure problem. The operator may ignore the problem because the operator assumes that some relatively time consuming remedial process would be required to eliminate the problem and fails to recognize the simple remedial step. In these cases it has been recognized that simply providing a list of possible pressure reducing sources that are easy to remedy can cause a xe2x80x9cdisturbancexe2x80x9d in the broadest sense as, faced with simple and minimal time consuming remedies, an operator will be compelled to attempt to remedy the pressure problem.
Consistent with the above comments, an exemplary embodiment of the invention includes an apparatus for protecting a vehicle operator within a cab of a mobile vehicle working in a polluted environment, the cab sealed from the polluted environment and including a pressure system for maintaining a cab pressure above a threshold pressure and a pressure sensor for generating an alarm signal when the cab pressure drops below the threshold pressure. The apparatus comprises a timer and a processor linked to the timer and for, when a first alarm signal is generated, disrupting operation of the vehicle, timing out a disrupt period and, at the end of the disrupt period, returning the vehicle to normal operation. In one embodiment, during the disrupt period, the processor monitors the alarm signal and, if the alarm signal ceases, returns the vehicle to normal operation.
In one aspect certain embodiments further including a communication device for communicating information to a vehicle operator and a memory device for storing information related to possible causes of cab pressure reduction. In these cases, the processor is linked to the communication device and the memory device and, when an alarm signal is generated, the processor retrieves the information and provides the information to the vehicle operator via the communication device. In some cases the information also includes a message that vehicle operation will remain disrupted for the duration of one disrupt period unless the cab pressure rises above the threshold pressure. In some cases the information includes a list of instructions guiding the vehicle operator to perform various tasks to increase the cab pressure to a point above the threshold pressure.
Where the vehicle includes an implement the processor may disrupt by disabling the implement and, in these cases, the processor may cause a marker or a vehicle location system (e.g., GPS) to mark location upon disabling the implement. In other cases the system may include an audible alarm and the processor may disrupt by activating the alarm. In still other cases the processor may disrupt by reducing the maximum vehicle speed.
The apparatus may further include an indicator and, in some cases, when the first alarm signal is generated, the processor may be programmed to activate the indicator and time out a delay period prior to disrupting vehicle operation.
The invention further includes an apparatus for protecting a vehicle operator within a cab of a mobile vehicle working in a polluted environment, the cab sealed from the polluted environment and including a pressure system for maintaining a cab pressure above a threshold pressure and a pressure sensor for generating an alarm signal when the cab pressure drops below the threshold pressure. Here the apparatus comprises a communication device for communicating information to the vehicle operator, a memory device for storing information related to possible causes of cab pressure reduction and a processor linked to the communication device and the memory device and for, when an alarm signal is generated, retrieving the instructions and providing the instructions to the vehicle operator via the communication device. Again, here, the information may include a list of instructions guiding the cab operator to perform various tasks to increase the cab pressure to a point above the threshold pressure.
In addition to the apparatus described above, the invention also includes methods that perform the processes that are performed above. The methods are described in greater detail in the specification that follows.
Thus, it should be appreciated that the present invention, upon cab depressurization, provides a hindrance that is calculated to tip the balance in favor of a tractor operator at least attempting to correct the pressure problem. Where the operator either decides not to correct the problem or attempts to correct the problem and the cab pressure does not increase to a desired level, the system automatically returns tractor operation to normal after a disrupt period so that operations can continue. In some embodiments the operator is, in effect, warned that operation will be disrupted at the end of a delay period so that the operator has the ability to effectively select where within a task being performed, the operator should halt vehicle operations to attempt to remedy the pressure problem.
These and other aspects of the invention will become apparent from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown a preferred embodiment of the invention. Such embodiment does not necessarily represent the full scope of the invention and reference is made therefore, to the claims herein for interpreting the scope of the invention.